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From kombucha to kimchi, fermented foods are on-trend. Niki Bezzant debunks the benefits.

There's an alien in my kitchen. It sits in a jar, quietly growing and having babies. It's my SCOBY - the Symbiotic Culture of Bacteria and Yeast that makes my kombucha.

Kombucha is the healthy beverage du jour. As well as multiplying in home kitchens, it's popping up in many brands in supermarket chillers and even on tap in pubs. It's a very simple fermented drink, made from tea and sugar; the SCOBY works its magic eating up the sugar and contributing potentially useful probiotics to the brew.

If you Google kombucha's health benefits you will find a long list of amazing things: it can, it's claimed, do everything from lowering cholesterol to fending off ageing.

Perhaps more believable are claims that kombucha - and other popular fermented foods, such as kimchi and sauerkraut - are beneficial for our gut bacteria, because of the probiotics they contain. Probiotics are so-called "good" bugs. They can be found in supplements, of course, which we're probably familiar with. But they're also in fermented foods such as kombucha, yoghurt, kefir and sourdough bread.

Gut bacteria has got scientists excited in recent years. We each carry around trillions of bacteria inside us; it performs vital functions such as helping us digest our food; making important vitamins; attacking infections and viruses and fighting off 'bad' bacteria. There's great interest in our gut bacteria in particular, because there's more and more evidence emerging that what goes on in our gut can affect many aspects of our health, from our immunity to our weight to our mental health.

Hence the renewed popularity of quite old-school fermented foods and drinks. Fermentation, after all, was an ancient way of preserving food in the days before refrigeration. It gave us cheese and wine, so it's a process to which we owe a lot.

So is this new-old batch of fermented foods really good for us? Should we load up on the kimchi and say yes the next time someone offers us a SCOBY?

Fermented foods, such as kimchi and sauerkraut - are beneficial for our gut bacteria, because of the probiotics they contain. Photo / Getty Images

It seems fair to say that what we don't know about probiotics - and particularly probiotics in food - is a lot more than what we do know. There's a vast range of probiotics; thousands of strains; and different strains have been found to do different things. Unless a particular brew of kombucha or kraut has been analysed, it's not really possible to say which strains it might contain, and whether or not those probiotics have been studied for particular effects is another thing again. So drinking a kombucha or eating sauerkraut for a specific health benefit might be a bit hit and miss.

It's also worth noting that there hasn't yet been a human trial testing out the health benefits of kombucha, specifically. Though there's some interesting laboratory research results suggesting possible benefits, we don't really know for sure. The same seems true for sauerkraut: it's promising, but needs more research.

For general health, though, there's probably some benefit to be had from fermented foods.

At the very least, you'll get the antioxidant benefit of the tea the kombucha is based on, and in the case of sauerkraut and kimchi, the healthy vegetables they're made from. Feeding your gut bacteria an ongoing mix of different types of fermented foods is not a bad idea. And as an alternative to alcoholic drinks, kombucha is a refreshing choice that's better than a sugary soft drink or juice.

But fermented foods are not a shortcut to good gut health. We can't sip kombucha instead of feeding our gut with a wide range of healthy foods. Those good bacteria especially like all kinds of fibre, so that means eating whole grains, legumes, seeds, nuts, vegetables and fruit on the regular.

If you're a convert to kombucha, keep an eye on the sugar. The sugar content in commercial versions can vary widely from almost nothing to quite a lot, and this plus the fact that it's acidic could mean drinking a lot of it might not be great for teeth. There are some alarming documented cases of quite serious harmful effects when home-made kombucha has been contaminated with bacteria or fungus. If you're making it yourself, make sure you follow instructions and keep containers sterilised, and if you're at all worried about the safety of a brew, throw it out.

If you're starting out on fermented foods or drinks, nutritionists recommend starting with small amounts at a time to see how your body tolerates them; don't chug a whole bottle of kombucha until you know it sits okay with you. I was interested to discover recently that large amounts (over 250ml) of kombucha contains enough fructans - one of the FODMAPs - to upset some people with IBS. So go easy when you start your fermented food adventure. Enjoy regular small doses of fermented goodness for their zing and variety and for the possible health they add to your diet.